1. Field of the Invention
The invention is directed to a bacteriostatic/cidal and anti-collagenolytic adhesive used to control the invasion and proliferation of microorganisms. In some embodiments, the invention is directed to an antimicrobial dental adhesive/restorative material used to control microbial pathogens within the oral cavity.
2. Background of the Invention
An attempt to manage two of the most common human maladies in the world, tooth decay and periodontal disease, must be waged in an environment that is continually bathed in saliva that is filled with thousands of bacterial species present as a complex population numbering in the hundreds of millions of bacteria per milliliter of salvia. In addition, this environment also includes a multitude of enzymes, minerals, yeasts, foodstuffs and more. Dentistry has made many advances in restorative materials and technology to manage these diseases. These advancements in adhesive dentistry and esthetic filling materials are certainly notable and significant. However, restoration durability remains a major problem.
It is estimated that over 70% of new dental restorations are a consequence of old dental restorations that have failed. In 2005, 166 million dental restorations were placed in the United States and it can be estimated that over 83 million of those were replacements of failed dental restorations. The most popular restorative material is resin based composite (RBC). RBC restorative materials are popular due to their excellent wear, lifelike esthetics and ability to conserve tooth structure.
Currently, 65% of restorations in the United States are made of RBC. RBC popularity is rising due to several factors but primarily by patient demand for esthetic restorations. Despite their popularity, RBC restorations have limited clinical longevity. It is estimated that the cost of replacement of failing composite restorations is 5 billion dollars annually. Bacterial infiltration is the most frequent complication of RBC restorations resulting in recurrent caries as the principle cause of failure.
In recognition of these shortcomings, Imazato and colleagues conducted a series of experiments where composite resins containing an antibacterial monomer, 12-methacryloyloxydodecylpyridinium bromide (MDPB) were evaluated for its ability to withstand the degradative and destructive activities manifested by cariogenic microbes present in the oral cavity. The bactericidal activity of the adhesive resin containing MDPB was evaluated by subjecting discs constructed of composite resin with and without MDPB in the presence of a cariogenic microbe, Streptococcus mutans. These studies were remarkable in that they found that the numbers of bacteria recovered from the discs containing MDPB were reduced by 97%. Imazato and colleagues also evaluated the tensile bond strength of the composite resin containing MDPB by utilizing extracted human molars that were free of restorations and carious lesions. They found that the tensile bond strength of the MDPB resin was not significantly different from that of the control. A resin based on this technology is disclosed in U.S. Pat. Nos. 5,733,949 and 6,355,704 and marketed under the name Clearfil™ SE Protect bond by Kuraray Dental (www.kuraray-am.com/).
However, while the technology disclosed in U.S. Pat. Nos. 5,733,949 and 6,355,704 attempts to minimize bacterial retention and invasion of dental bonding agents, certain deficiencies continue to exist. Little evidence exists on the longevity of MDPB's antimicrobial activity and it has been suggested that it is short lived possibly due to decreased antimicrobial activity after light curing. Indeed, much of the independent research that shows MDPB has antimicrobial activity against oral microorganism did not use polymerized MDPB and thus does not correlate accurately to the clinical situation which necessitates polymerization of the MDPB adhesive resin.
Likewise, glass ionomer (GI) has always been touted for its bacteriostatic effect due to high concentrations of fluoride release. However, some research data indicates that while they do limit bacterial proliferation, it is not entirely antimicrobial. This is especially true because GI's antimicrobial properties are a function of the release of fluoride which is a component of the GI matrix. Thus, as the restoration ages, fluoride release decreases. In addition, poor antimicrobial resistance coupled with glass ionomer's recognized deficiencies including poor resistance to surface wear and poor resistance to fracturing means that bacterial invasion of the restoration is an ongoing process undermining the longevity of the restoration itself.
Therefore, a more efficacious and longer-lasting bacteriostatic and/or bacteriocidal agent for use in biological implants, especially dental ones, are needed.